Automatic pinfall detecting apparatus for bowling game



3,091,456 AUTOMATIC'Y'IPINFALL DETECTING APPARATUS FOR BOWLING GAME Filed Sept. 15, 1961 G. H. BRODIE May 28, 1963 2 Sheets-Sheet 1 FiqJ VII 7 RECTIFIER AMPLIFIER ANALOG TO DIGITAL CONVERTER INVENTOR.

George H.Brodie Fig.3

ATTORNEY y 8, 1963 G. H. BRODIE 3,091,456

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ATTORNEY United States Patent 3,091,456 AUTOMATIC PINFALL DETECTING APPARATUS FOR BGWLENG GAME George H. Brodie, Pepper Pike, Ghio, assiguor, by mesnc assignments, to Cleveland Trust (10., trustee, Cleveland, Ohio Filed Sept. 15, 1961, Ser. No. 138,349 12 Claims. (Cl. 273--54) This invention relates to apparatus for automatically detecting the number of pins knocked down after each ball is rolled in a bowling game. More particularly, the invention relates to apparatus of the type described adapted to produce electrical signals which may be used to automatically score, totalize, visually indicate and/or print the totalized score.

Although the present invention is shown herein in combination with apparatus for simply indicating the number of pins knocked down by a ball in a bowling game, it IS particularly adapted for use with an automatic scoring, totalizing and printing system for a bowling game such as that shown in copending application Serial No. 38,091, filed July 7, 1960, wherein the pinfall for each ball, the frame-by-frame score and the total score are printed on a permanent score sheet. In such a system it is, of course, first necessary to obtain an accurate indication of pinfall after each ball is rolled; and although the problem of obtaining an accurate pinfall indication may appear simple at first, it is complicated by the fact that after a ball is rolled in a bowling game, certain of the pins will slide on the pin deck without being knocked over. Consequently, the use of simple limit switches, photocells or the like which are fixed in position are unsatisfactory for the purpose of obtaining pinfall if an absolutely fail-proof system is to be devised, such as that required for scoring the game.

As an overall object, the present invention seeks to provide new and improved apparatus for automatically and accurately indicating the number of pins knocked down by each ball in a bowling game.

More specifically, an object of the invention is to provide a system for producing an electrical signal indicative of the number of pins knocked down by a bowling ball, which will function properly to give a true indication of pinfall regardless of whether any standing pins on the alley are misplaced due to sliding or other causes.

Another object of the invention is to provide pinfall detecting apparatus for a bowling game capable of producing electrical signals which may be used in an auto matic scoring, totalizing, indicating and/ or printing systern.

Still another object of the invention is to provide a bowling pin configuration which may be electrically detected by a bridging capacity effect.

In accordance with the invention, pinfall is detected by creating electric fields between spaced capacitor plates on the surface of the pin deck and by providing electrical conducting material on the bottom of each pin such that the conducting material will produce a bridging capacity effect across two or more plates when the pin is standing, but not when it has been knocked down by a ball. Thus, the total capacitance of the capacitor plates on the pin deck will be a function of the number of standing pins, and by measuring the change in capacitance in response to one or more pins being knocked down by a ball, the number of fallen pins may be determined. Preferably, the capacitor plates comprise parallel strips of electrical conducting material which are imbedded in the pin deck slightly below the surface thereof to offer protection from abrasion by fiying pins and speeding bowling balls. By interconnecting alternate ones of the strips to the opposite 3,991,455 Patented May 28, I963 terminals of a source of variable amplitude voltage, the strips will act as the opposite plates of a capacitor. The conducting material at the bottom of each pin is preferably a metal foil insert in the pin base having an area great enough to effect a bridging capacity effect between two or more of the parallel strips such that the capacity of the arrangement will be decreased as each pin is knocked down. With a suitable circuit, the amount of change in capacity can be read out as a change in voltage, and may then be converted into a discrete number of pulses which, in turn, may be utilized to indicate the number of fallen pins or to totalize and indicate or print the bowling game score.

The above and other objects and features of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings which form a part of this specification and, in which:

FIGURE 1 is a top view of a bowling alley pin deck having the parallel conductive strips of the invention imbedded therein for the purpose of producing electric fields across the surface of the pin deck;

FIG. 2 is a partially broken-away cross-sectional view taken substantially along line II-II of FIG. 1 showing a bowling pin with a metal foil insert at the bottom thereof for the purpose of producing a bridging capacity effect bet-ween two or more of the parallel electrical conductors shown in FIG. 1;

FIG. 3 is an illustration of one type of circuit for converting a change in capacity between the parallel conductors of FIG. 1 in response to pins being knocked down by a bowling ball into a proportional number of electrical impulses, this circuit being based on a simple reactance type measurement;

FIG. 4 is an illustration of another type of circuit for converting a change in capacitance of the strips shown in FIG. 1 into a proportional number of electrical impulses, this circuit utilizing a fixed charging pulse feeding through the variable capacity of the parallel strips, and balanced against a reference channel to give a differential reading;

FIG. 5 is an illustration of a circuit for converting a change in capacitance of the strips in FIG. 1 into a proportional number of impulses and employing a capacity bridge measurement readout; and

FIG. 6 is an ilustration of still another circuit for converting the change in capacitance of the strips in FIG. 1 into a proportional number of impulses, this circuit being based on a frequency bridge type measurement.

Referring now to FIGS. 1 and 2, the usual bowling alley is shown having a pin deck 12 with ten pins positioned thereon in the usual triangular configuration and numbered 1 through 10. On either side of the pin deck 12 are two gutters 14 and 16, while behind the pin deck 12 is a pit 18.

In accordance with the present invention, a plurality of parallel ribbons of electrical conducting material such as copper, generally indicated at 20, are spaced at equal intervals across the entire width of the pin deck 12, it being understood that only a portion of the ribbons are shown in FIG. 1 for purposes of illustration. Alternatively, the conducting ribbons could be spaced at right angles to the direction shown in FIG. 1. In either case, alternate ones of the conducting strips will be connected to a first lead 22 on one side of the pin deck while the remaining alternate ones of the conducting strips will be connected to a second lead 24. In FIG. 2, the conducting strips connected to lead 22 are designated by the reference numerals 20A; while those connected to lead 24 are designated by the numerals 20B. Preferably, the conducting strips comprise thin ribbons of copper or other u: material of high electrical conductivity. By connecting the respective leads 22 and 24 to a source of alternating current voltage, or any source of variable amplitude voltage, electric fields will be produced between adjacent edges of successive strips ZtiA, 2M3. The wooden surface of the pin deck 12 is preferably varnished to insulate the bottoms of the thin metal ribbons (the thickness of which is exaggerated in FIG. 2); while the tops of the ribbons may be insulated from each other by means of a varnish or by a thin plastic covering, the only requirement being that the strips be protected from abrasion by flying pins and speeding bowling balls.

As shown in FIG. 2, each of the pins numbered 1 through is provided with a circular metal foil insert 26 in its base, the foil insert being insulated from the bottom of the pin by means of an insulating spacer 28. Since each of the pins 1 through 10 is provided with a metal insert, and since each of the inserts is of the same area, the total capacitance of the strips 20 between leads 22 and 24 will be increased in equal increments as each pin is placed on the deck 12 in an upright position. Similarly, as each pin is knockeddown on the pin deck 12,. its metal foil insert 26 can no longer produce a bridging capacity effect so that the pin is no longer effective in increasing the total capacitance between leads 22 and 24. Thus, by measuring the capacity between leads 22 and 24 with circuitry such as that hereinafter described, the number of standing or fallen pins can be determined.

It is, of course, desirable to effect as large a capacity change as possible between leads 22 and 24 when a bowling pin is knocked down. Accordingly, the smallest number of interleaved conductors 2% should be employed so as to minimize the overall capacitance of the arrange ment. At the same time, the conducting strips 20A and 20B should be spaced such that the metal foil inserts 26 in the bottom of each pin may produce an efiective bridging capacity effect. Assuming that the diameter of each pin base is two inches, it has been found desirable to provide foil strips 20A and 20B having a width of threequarters of an nich, with the ribbons being spaced onequa-rter inch apart. With this arrangement, the metal foil insert 26 in each pin will bridge across at least two of the gaps between successive ribbons 20A and 20B; and the capacity change per pin will run very close to 10 mmf. That is, there will be a capacity increase of 10 mmf. between leads 22 and 24 as each pin is placed on the pin deck; and, similarly, there will be a decrease of 10 mmf. between leads 22 and 24 as each pin is knocked down. Thus, if only one pin is knocked down by a ball, there will be a capacity decrease of 10 mmf; if three pins are knocked down there will be a capacity decrease of 30 mmf.; if five pins are knocked down there will be a capacity decrease of 50 rnmf; and so on.

It is, of course, desirable to operate the grid formed by strips 20 at the highest possible frequency; however if the frequency becomes too high, a standing wave of voltage becomes a problem. For example, with three-quarter inch strips spaced one-quarter inch apart across the deck 12, the grid appears to act somewhat like a transmission line or antenna at 100 kilocycles, with a standing wave of voltage existing across it amounting to about a five to one ratio. At 10 kilocycles or lower, this problem is reduced to reasonable proportions. Accordingly, in certain cases it may be desirable to split up the grid into four or five sections and successively scan those sections to enable the grid to be operated at higher frequencies.

Referring now to FIG. 3, one method for converting the change in capacity of the grid 20 into a proportional number of voltage impulses is shown wherein the grid is connected in parallel with an impedance, such as resistor 28. Connected between the terminals of the grid 2% and resistor 28 are a source of alternating current voltage 30' and a capacitor 32, it being understood that the source 30 may alternatively comprise any type of variable amplitude voltage, such as that produced by a pulse generator. The voltage across resistor 28 is then amplified in amplifier 34 and rectified in rectifier 36, the output of rectifier 36 being a direct current voltage which varies as a function of the total capacitance of grid 20. This capacitance, in turn, is a function of the number of standing pins as was explained above. The output of rectifier 36 is then applied to an analog-to-digital converter 38 which will produce a number of voltage pulses or digits on lead 40 proportional to the change in direct current voltage from rectifier 36. This change in voltage, in turn, is proportional to a change in the number of standing pins on grid 20. Thus, in the usual bowling game, after one or more pins have been knocked down by a ball, the capacity of grid 20 will decrease, its impedance will increase, and the current through resistor 28 will decrease. This decrease in current is reflected as a change in voltage at the output of rectifier 36 which is converted into a proportional number of pulses on lead 4th Thus, if three pins are knocked down by a ball, the analog-to-digital converter 33 is such that it will produce three pulses on lead 40; if five pins are knocked down, five pulses will be produced on lead 40; and so on. These pulses are applied to a stepper switch 42 comprising a solenoid 44 connected to a pawl 46 which advances a ratchet 48 each time the solenoid 44 is energized in response to a pulse on lead 40. The ratchet 48, in turn, is connected to a wiper brush 50 on a circular index 52. The index 52 has ten contact points thereon numbered 0 through 10. Each of these contacts is connected through an associated lamp 54 to one terminal 56 of a voltage source, the other terminal 58 of the voltage source being connected to the rotary wiper brush 50 as shown. Thus, assuming that three pins have been knocked down, the Wiper brush will be advanced to the number 3 contact on index 52, thereby energizing the lamp connected to that contact to indicate that three pins have been knocked down. Similarly, if ten pins have been knocked down, the solenoid 44 Will be energized ten times to advance the wiper brush 50 to the number .10 contact to energize its associated lamp to indicate the number of pins knocked down. The ratchet 48 is spring loaded, and the indicating apparatus may be reset by energizing solenoid 60 after each frame or ball to disengage the pawl 46 from ratchet 48 to permit that ratchet to spring back to its original position where the wiper brush 50 is on the zero contact.

As will be understood, the indicating apparatus shown herein is illustrative of only one type of indicating arrangement which may be employed and does not produce an indication of the number of pins knocked down by the first and second balls, respectively, in a frame, but only the cumulative number of pins for a frame. The apparatus of the invention may, however, be employed in apparatus such as that shown in copending application Serial No. 60,350, filed October 4, 1960 and now abandoned, or the aforesaid application Serial No. 38,091, filed July 7, 1960 for the purpose of indicating the number of pins knocked down by the first and second balls, respectively, or in apparatus for automatically totalizing and printing the score in the bowling game in response to the number of pins which have been detected as being knocked down by the grid 20 and its associated circuitry.

Referring now to FIG. 4, another circuit is shown for converting a change in capacity in response to a number of pins being knocked down into a proportional number of voltage impulses or digits. In this case, the lead 22 on grid 20 is connected to one output terminal of a pulse generator 62 while the other lead 24 is connected through a diode 64 and capacitor 66 to the other output terminal of the pulse generator. Connected in parallel with capacitor66 is a resistor 68 having a movable tap 70 thereon which is connected to one input terminal of a differential amplifier '72. The other input terminal of the differential amplifier 72 is connected as shown to the side of pulse generator 62 connected to lead 22. Connected to lead 24 through diode 74 is a source of voltage, identified as B+, which serves to prevent the voltage on lead 24 from talling below a predetermined negative value.

The output of pulse generator 62 will be a train of voltage pulses of a predetermined fixed amplitude; while the pulses appearing across capacitor 66 and resistor 68 will be those from pulse generator 62 which have been attenuated and reduced in amplitude, the reduction in amplitude being proportional to the capacitance of the grid 20. This capacitance, of course, is a function of the number of standing pins, the greater the number of standing pins, the greater the capacitance and the less the attenuation. By comparing the attenuated pulses across resistor 68 with the original, unattenuated pulses from generator 52 in differential amplifier 72, and by adjusting the differential amplifier so that zero output voltage will be produced on its output lead 75 when all ten pins are standing on grid 20, the amplitude of the pulses on lead 75 will vary as a function of the number of fallen pins. These pulses are then rectified in rectifier 76 and passed to an analog-to-digital converter 78 which functions in the same manner as the analog-todigital converter 38 shown in FIG. 3. The output of the converter 78 may then be passed to indicating apparatus such as that shown in FIG. 3.

Referring now to FIG. 5, another circuit is shown wherein the grid 20 is connected in a bridge circuit, two of the diagonally opposite impedances of which comprise the grid 20 itself and a resistor 80, while the other two diagonally opposite impedances comprise a resistor 82 and a series of parallel-connected capacitors 84A-84K. The capacitor 84A is permanently connected in the bridge circuit and has a capacitance equal to that of the capacitance of grid 20 with all of the ten pins standing. The remaining capacitors 84B-84K are ten in number, with each capacitor having a capacitance equal to the capacitance due to a standing pin (i.e., about mmf.). Each of the capacitors 34B-84K is adapted to be connected into the bridge circuit through the normally closed contacts 85 of an associated normally deenergized relay 86B-86K. As will be seen, a number of relays 8613- 86K will be energized corresponding to the number of pins knocked down, thereby opening their associated contacts 85 to disconnect a number of capacitors MB-84K from the circuit corresponding to the number of tallen pins. As was mentioned above, each of the capacitors 84B-84K has a capacitance equal to the capacitance effected by a standing pin. Thus, as each pin is knocked over, a corresponding one of the capacitors 84B84K will be disconnected from the circuit to compensate for the knocked down pins and again balance the bridge circuit.

Connected across the input terminals of the bridge circuit is a source of alternating current voltage 88 while an output signal is taken from the output terminals of the bridge circuit via lead 90 and ground. This output signal is amplified in amplifier 92 and applied to one phase or winding 94 of a two-phase servomotor 96, the other phase or winding 98 of which is connected to the output terminals of alternating current voltage source 88. Connected to the shaft of servomotor 96 is a wiper drum 100 which comprises a cylinder of conducting material having insulation on its surface except for a plurality of strips 102 which gradually increase in circumferential length along the axis of the drum. The drum itself is connected to one terminal of a voltage source, as at 103. Each of the strips 102 on drum 100 is adapted to contact a wiper brush 104 connected to the energizing circuit for one of the relays 86B-86K. Thus, as the drum 100' is rotated by the servomotor 96 in one direction, for example, the conducting strip 102 for the brush 104 associated with relay 86B will be contacted first to energize this relay and maintain it energized; the wiper brush 104 for relay 860 will be contacted next; the wiper brush for relay 86D will be contacted next; and so on. Thus, as the servomotor rotates in one direction each of the relays 86B-86K will be energized in succession and will remain energized until the servomotor is rotated in the opposite direction, during which time the relays 86B-86K will be deenergized in the reverse order. As each relay 86B- 86K is energized it will, of course, open its normally closed contacts to disconnect its associated capacitor 84B-84K from the circuit to compensate for knocked down pins.

Also connected to the shaft of servomotor 96 is the wiper brush 1% of an index 108 having ten contact points thereon, each of which is connected to an associated lamp 10 to indicate the number of fallen pins in the manner described in connection with the circuit of HG. 3.

In the operation of the circuit of FIG. 5, when all of the ten pins are standing, the reactance of the grid 20 will .be balanced by the reactance of fixed capacitor 84A; and no output signal will appear on lead 90 to rotate the servomotor 96. When, however, one or more pins are knocked down by a ball in a bowling game, the reactance of grid 20 will be altered, thereby unbal-ancing the bridge to produce an output signal on lead .90 which is applied to the winding 94 of servomotor 96 to rotate it in one direction lwhereby one or more of the brushes 104 will contact the strips 102 on drum 100. The number of brushes 104 which contact the strips .102 will be dependent upon the number of degrees of rotation of servomotor 96; and this, in turn, is dependent upon the number of fallen pins. Thus, the servomotor 96 will rotate to sequentially switch capacitors out of the bridge circuit until the bridge is again balanced, at which time the servomotor 96 stops. Assuming that five pins have been knocked down by a ball, the servomotor will have been rotated to energize relays 86 13-861 At this time, the wiper bnush 105 will be on the fifth contact on index 108 to energize its corresponding lamp to indicate that five pins have been knocked down.

When the pins are again placed on the grid 20, its capacitance will increase and its react-ance decrease, thereby again unbalancing the bridge to produce an output signal on lead 90. In this case, however, the output signal on lead 90 will have a phase opposite to that which was produced when pins were knocked down. Accordingly, the servomotor 96 will be rotated in the opposite direction to close the contacts associated with all of the capacitors 8413-8414; and after all contacts have been closed, the bridge will again be balanced so that the servomotor 96 will be stopped with the wiper brush 106 on the zero contact on index 108. Thus, as pins are placed on or removed from the grid 20, the servomotor 96 will be rotated in one direction or the other to switch into or out of the circuit the corresponding number of capacitors 84B-84K to again balance the bridge circuit, while at the same time moving the wiper brush 106 to the proper contact point on index 103 to indicate the number of fallen pins.

Referring now to FIG. 6, another circuit is shown wherein the grid 25 is again connected in a bridge circuit, the grid and a resistor 110 of which comprise two of the diagonally opposite legs of the bridge; while resistors 112 and 114 comprise the other two diagonally opposite legs. Connected across the input terminals of the bridge circuit is a variable frequency oscillator 116 having a variable capacitor 118 in its tank circuit 120. An output signal is taken from the bridge between lead 122 and ground. This signal is amplified in amplifier 124 and applied to a motor control circuit 126 to rotate motor '128 which is connected through linkage 130 to capacitor 118 to vary the capacitance thereof. The motor 128 is also connected to the wiper brush 132 on an index 134 having a plurality of contact points thereon, each of which is connected to an associated lamp 13s to indicate the number of fallen pins.

In the operation of the circuit of FIG. 6, with all pins standing on the grid 2!}, the bridge circuit will be balanced. When, however, one or more of thepins are knocked down by a ball in a bowling game, the bridge will become unbalanced and an output signal will appear on lead 122. This output signal will actuate motor 128 through motor control circuit 12-6 to vary the capacitance of capacitor 1118, thereby varying the frequency applied across the input terminals of the bridge circuit. The reactance of the grid 20, being equal to 1 21rfc where f is the frequency of oscillator 116 and c is the capacitance of grid 20, may be varied by varying the frequency of oscillator 116. Thus, the output signal on lead 122 will rotate motor 128 until the capacitance of capacitor 118 is such as to produce a frequency at the output of oscillator 116 where the reactance of grid 20 is such as to again bring the bridge back into balance, at which time the signal on lead 122 will disappear and the motor will stop with the wiper :brush 132 on the correct contact point to indicate the number of fallen pins.

As in the embodiment of FIG. 5, when the pins are again placed on the grid 29, the bridge circuit will again become unbalanced, but the phase of the signal on lead 122 will be reversed so that motor 128 will be rotated in the opposite direction to vary the capacitance of capacitor 118 and change the frequency ct oscillator 116 back to its original value where the bridge is again balanced and the wiper brush 132 is on the zero contact.

Although the invention has been shown in connection with certain specific embodiments, it will be readily apparent to those skilled in the art that various changes in form and arrangement of parts may be made to suit requirements without departing from the spirit and scope of the invention.

I claim as my invention:

1. In a bowling game, apparatus for determining the number of pins knocked down on an alley comprising a plurality of parallel electrical conducting strips positioned on said alley beneath said pins, each of said strips extending tor the entire length of the pin deck on which the pins are positioned, a source of variable amplitude voltage having a pair of output terminals, means coupling one of said terminals to alternate ones of said conducting strips, means coupling the other of said terminals to the remaining ones of said conducting strips whereby the conducting strips coupled to the respective terminals will function as the opposite plates of a single capacitor, conducting material on the bottoms of said pins whereby the conducting material on any standing pin will efiect a bridging capacity effect across two or more of the conducting strips to vary the total capacitance of the single capacitor termed by the strips, means for measuring a change in total capacitance of the strips in response to a change in the number of standing pins, and means for visually indicating said change in capacitance to thereby also indicate the number of standing pins.

2. The apparatus of claim 1 wherein the parallel electrical conducting strips are imbedded in the alley slightly below the surface thereof and wherein the conducting material on the bottom of each pin comprises a sheet of conducting material which lies in a plane extending parallel to the surface of the alley when the pin is in an upright position.

3. In a bowling game, apparatus for determining the number of pins knocked down on an alley comprising a plurality of parallel electrical conducting strips positioned on said alley beneath said pins, each of said strips extending throughout the entire length of one dimension of the pin deck on which the pins are positioned, a source of variable amplitude voltage having a pair of output terminals, means coupling one of said terminals to alternate ones of said conducting strips, means coupling the other of said terminals to the remaining ones of said conducting strips whereby .the conducting strips connected to the respective terminals will function as the opposite plates of a single capacitor, conducting material on the bottoms of said pins whereby the conducting material on any standing pin will eiiect a bridging capacity effect across two or more of the conducting strips to vary the total capacitance of the single capacitor formed by the strips, an impedance element connected in shunt across the capacitor formed by said conducting strips, means for rectifying the variable amplitude signal appearing across said impedance element, means responsive to the rectified voltage from said rectifier for producing a number of voltage pulses proportional to the magnitude of said rectified voltage, the arrangement being such that the number of pulses produced will be equal to the number of pins knocked down after the rolling of a ball in a bowling game, and means for visually indicating said number of pulses.

4. In a bowling game, apparatus for determining the number of pins knocked down by a ball comprising a plurality of parallel electrical conducting strips positioned on said alley beneath said pins, electrical conducting material in the bottoms of said pins, said conducting material being insulated from the strips, 21 pulse generator having a pair of output terminals, means connecting one of said terminals to alternate ones of said conducting strips, a capacitor connecting the other of said terminals to the remaining ones of said conducting strips whereby the conducting strips connected to the respective terminals will function as the opposite plates of a capacitor, differential amplifier means for comparing a fixed portion of the pulses at the output of said pulse generator with the pulses appearing across said first-mentioned capacitor whereby the output of the differential amplifier will be pulses having an amplitude equal to the difference in amplitude between the pulses compared thereby, means for rectifying the pulses at the output of said differential amplifier means, means for producing a number of pulses proportional to a change in the output voltage of said rectifier, the arrangement being such that the number of pulses thus produced Will be proportional to the number of pins knocked down by a bowling ball in a bowling game, and apparatus responsive to said last-named pulses for visually indicating the number of pins knocked down by a bowling ball in a bowling game.

5. The apparatus of claim 4 wherein said first-mentioned capacitor and a pulsating unidirectional current device connect the other of said terminals to the remain ing ones of said conducting strips.

6 In a bowling game, apparatus for determining the number of pins knocked down on an alley by a ball comprising a plurality of electrical conducting strips positioned on said alley beneath said pins, each of said strips extending throughout the entire length or" one dimension of the pin deck on which the pins are positioned, first means interconnecting alternate ones of said conducting strips, second means interconnecting the remaining ones of the conducting strips whereby the respective interconnected strips will act as the opposite plates of a single capacitor when a source of variable voltage is connected to the respective interconnected strips, conducting material on the bottoms of said pins whereby the conducting material on any standing pin will effect a bridging capacity effect across two or more of the conducting strips to vary the total capacitance of the single capacitor formed by the strips, means connecting the respective interconnected strips in a bridge circuit whereby a change in capacitance of the single capacitor formed by the strips will be reflected as an unbalancing of the bridge, and means for visually indicating the unbalance in the bridge to thereby indicate the number of standing pins.

7. The apparatus of claim 6 wherein the capacitor formed by the respective interconnected strips comprises one leg of the bridge circuit, and including variable capacitance means in another leg of the bridge circuit whereby the capacitance of the variable capacitance means may be altered to again balance the bridge in response to one or more pins being knocked down by a bowling ball.

8. In a bowling game, apparatus for determining the number of pins knocked down on an alley by a ball comprising a plurality of parallel electrical conducting strips positioned on said alley beneath said pins, first means interconnecting alternate ones of said conducting strips, second means interconnecting the remaining ones of the conducting strips whereby the respective interconnected strips will act as the opposite plates of a capacitor when a source of variable voltage is connected to the respective interconnected strips, conducting material on the bottom-s of said pins whereby the conducting material on any standing pin will efiect a bridging capacity effect across two or more of the conducting strips to vary the total capacitance of the capacitor formed by the strips, the combination of a variable impedance and a pair of fixed impedances connected in series between the respective interconnected strips on the bowling alley, a source of variable voltage connected between one set of interconnected strips and the junction of said fixed impedances, means for deriving an output signal between the other of said interconnected strips and the junction of said variable impedance and one of said fixed impedances, means including a servomotor device responsive to said output signal for varying the impedance of said variable impedance means upon notation of the servomotor device until the output signal is reduced to zero and the servornotor device stops, and means coupled to said servomotor device for indicating the number of pins knocked down by a ball as a function of the amount of rotation of the servomotor device before it stops.

9. In a bowling game, apparatus for determining the number of pins knocked down on an alley by a ball comprising a plurality of parallel electrical conducting strips positioned on said alley beneath said pin-s, first means interconnecting alternate ones of said conducting strips, second means interconnecting the remaining ones of the conducting strips whereby the respective interconnected strips will act as the opposite plates of a capacitor when a source of variable voltage is connected to the respective interconnected strips, conducting material on the bottoms of said pins whereby the conducting material on any standing pin will effect a bridging capacity effect across two or more of the conducting strips to vary the total capacitance of the capacitor formed by the strips, a bridge circuit having the capacitor formed by said parallel strips and a fixed impedance as two of its diagonally opposite legs, said bridge circuit having a second fixed impedance and variable capacitance means as its other two diagonally opposite legs, a source of variable amplitude voltage connected between the junction of said fixed impedances in the bridge circuit and the junction of the capacitor formed by said strips and said variable capacitance means, means for deriving an output signal from the bridge circuit such that the output signal will be zero when the capacitance of the conducting strips equals that of the variable capacitance means, means responsive to an output signal from said bridge circuit for altering the capacitance of said variable capacitance means until the bridge circuit is again balanced, and means for indicating the magnitude of the output signal from the bridge circuit, the arrangement being such that the magnitude of the output signal will be proportional to the number of pins knocked down by a ball.

10. In a bowling game, apparatus for determining the number of pins knocked down on an alley by a ball comprising a plurality of parallel electrical conducting strips a .19 positioned on said alley beneath said pins, first means interconnecting alternate ones of said conducting strips, second means interconnecting the remaining ones of the conducting strips whereby the respective interconnected strips will act as the opposite plates of a capacitor when a source of variable voltage is connected to the respective interconnected strips, conducting material on the bottoms of said pins whereby the conducting material on any standing pin will effect a bridging capacity effect across two or more .of the conducting strips to vary the total capacitance of the capacitor formed by the strips, means connecting the respective interconnected strips in a bridge circuit having variable capacitance means therein, means for deriving an output signal from the bridge circuit such that the output signal will be zero :at all times except when the bridge circuit is unbalanced in response to one or more pins being knocked down by a ball, means responsive to the output signal from the bridge circuit for changing the capacitance of said variable capacitance means in the bridge circuit to again balance the bridge circuit after one or more pins have been knocked down by a ball, and means for indicating the magnitude of the change in the capacitance of said variable capacitance means to again balance the bridge circuit, the arrangement being such that the magnitude of the change in capacitance will be proportional to the number of pins knocked down.

11. In a bowling game, apparatus for determining the number of pins knocked down on an alley by a ball comprising a plurality of parallel electrical conducting strips positioned on said alley beneath said pins, first means interconnecting alternate ones of said conducting strips, second means interconnecting the remaining ones of the conducting strips whereby the respective interconnected strips will act as the opposite plates of a capacitor when a source of variable voltage is connected to the respective interconnected strips, conducting material on the bottoms of said pins whereby the conducting material on any standing pin will effect a bridging capacity effect across two or more of the conducting strips to vary the total capacitance of the capacitor formed by the strips, means connecting the respective interconnected strips in a bridge circuit in which the strips form one leg of the bridge circuit :and resistor elements comprise the other three legs, means for applying a source of oscillatory voltage to the bridge circuit, means for deriving an output signal from the bridge circuit whereby the output signal will be zero when the bridge circuit is balanced, means responsive to an output signal from said bridge circuit for varying the frequency of said oscillatory voltage source until the bridge circuit is again balanced, the arrangement being such that the magnitude of the frequency shift required to again balance the bridge circuit will be proportional to the number of pins knocked down by a bail, and means for visually indicating the magnitude of said frequency shift and hence the number of pins knocked down.

12.. In a bowling game, apparatus for determining the number of pins knocked down on an alley by a ball com prising a plurality of parallel electrical conducting strips positioned on said alley beneath said pins, each of said strips extending throughout the entire length of one dimension of the pin deck on which the pins are positioned, first means interconnecting alternate ones of said conducting strips, second means interconnecting the remaining ones of the conducting strips whereby the respective interconnected strips will act as the opposite plates of a single capacitor when a source of variable voltage is connected to the respective interconnected strips, conducting material on the bottoms of said pins whereby the conducting material on any standing pin will effect a bridging capacity efiect across two or more of the conducting strips to vary the total capacitance of the single capacitor formed 11 12 by the strips, means for measuring a change in capacitance References Cited in the file of this patent of the single capacitor formed by the strips, the arrange- UNITED STATES PATENTS ment being such that the Inagnitude of the variation in 2,973,206: Sanders Feb. 28 1961 capacitance W111 be proportional to the number of pins 2974 955 Walsh 14 1961 knocked down by a ball, and means for visually indicating 5 298O424 Sanders- 1961 the change in capacitance to thereby indicate the number 2:988:359 Dettman June 1961 of Pins knocked down by a ball- 3,011,785 Torresen Dec. 5, 1961 

1. IN A BOWLING GAME, APPARTUS FOR DETERMINING THE NUMBER OF PINS KNOCKED DOWN ON AN ALLEY COMPRISING A PLURALITY OF PARALLEL ELECTRICAL CONDUCTING STRIPS POSITIONED ON SAID ALLEY BENEATH SAID PINS, EACH OF SAID STRIPS EXTENDING FOR THE ENTIRE LENGTH OF THE PIN DECK ON WHICH THE PINS ARE POSITIONED, A SOURCE OF VARIABLE AMPLITUDE VOLTAGE HAVING A PAIR OF OUTPUT TERMINALS, MEANS COUPLING ONE OF SAID TERMINALS TO ALTERNATE ONES OF SAID CONDUCTING STRIPS, MEANS COUPLING THE OTHER OF SAID TERMINALS TO THE REMAINING ONES OF SAID CONDUCTING STRIPS WHEREBY THE CONDUCTING STRIPS COUPLED TO THE RESPECTIVE TERMINALS WILL FUNCTION AS THE PLATES OF A SINGLE CAPACITOR, CONDUCTING MATERIAL ON THE BOTTOMS OF SAID PINS WHEREBY THE CONDUCTING MATERIAL ON ANY STANDING PIN WILL EFFECT A 